Bulgaria (България) is a country located in Southeastern Europe. It is bordered by Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south and the Black Sea to the east. With a territory of 110,994 square kilometres (42,855 sq mi), Bulgaria is Europe's 14th-largest country. Its location has made it a historical crossroad for various civilisations and as such it is the home of some of the earliest metalworking, religious and other cultural artifacts in the world.
Prehistoric cultures began developing on Bulgarian lands during the Neolithic period. Its ancient history was marked by the presence of the Thracians, and later by the Greeks and Romans. The emergence of a unified Bulgarian ethnicity and state dates back to the First Bulgarian Empire, which dominated most of the Balkans and functioned as a cultural hub for Slavic peoples during the Middle Ages. With the downfall of the Second Bulgarian Empire in 1396, its territories came under Ottoman rule for nearly five centuries. The Russo-Turkish War of 1877–1878 resulted in the Third Bulgarian State, recognised in 1908. The following years saw several conflicts with its neighbours, which prompted Bulgaria to align with Germany in both World Wars. In 1946 it became a Communist republic with a single-party system until 1989, when the Communist Party allowed multi-party elections. After 1990 Bulgaria transitioned to democracy and a market-based economy.
The population of 7.36 million people is predominantly urban and mainly concentrated in the administrative centres of its 28 provinces. Most commercial and cultural activities are concentrated in the capital Sofia. The strongest sectors of the economy are heavy industry, power engineering and agriculture, all relying on local natural resources.
The current political structure dates to the adoption of a democratic constitution in 1991. Bulgaria is a unitary parliamentary republic with a high degree of political, administrative and economic centralisation. It is a member of the European Union, NATO and the Council of Europe, a founding state of the Organization for Security and Co-operation in Europe (OSCE), and has taken a seat at the UN Security Council three times.